1. Field of the Invention
The present invention relates to a nitride semiconductor device and a method for fabricating the same, and more particularly, to a nitride semiconductor device and a method for fabricating the same, wherein a crack or damage that may occur in a nitride semiconductor unit device during a laser lift-off process can be minimized.
2. Description of the Related Art
Generally, a sapphire substrate is mainly employed as a substrate for nitride semiconductor growth. However, there are many difficulties in fabricating devices using nitrides due to the inherent conductivity of sapphire. Further, since the thermal conductivity of the sapphire is greatly inferior to other materials, it causes significant problems in driving the devices.
To solve these problems, a laser lift-off (LLO) method has been used conventionally.
The LLO method also has a disadvantage in that an entire sapphire substrate cannot be removed at a time due to limitations on the size and uniformity of a laser beam. Thus, a uniform but small sized laser beam is radiated on the sapphire substrate in a scanning manner to sequentially remove the substrate little by little.
However, non-uniformity is produced at an area of a separated device on which the laser beam has been radiated overlappingly. Thus, a crack produced due to this non-uniformity propagates into other areas of the device.
To prevent such a phenomenon, there has been used a method in which a part of a nitride layer is etched to separate each device that in turn is bonded to a Si substrate, a GaAs substrate, a metallic plate or the like, and a sapphire substrate is then removed therefrom.
However, air remaining in voids, which have been formed in trenches between the respective devices after the bonding process, expands due to intense laser energy and then creates cracks in the devices.